Laser conditioning mechanism in DKDP crystals analyzed by fluorescence and stimulated Raman scattering technique

In order to analyze the mechanism of damage threshold enhancement after laser conditioning, the stimulated Raman scattering and fluorescent properties of un-conditioned and laser conditioned of DKDP crystals were compared in detail. It revealed that the intensity of Raman scattering peak 921cm-1 were slightly lowered, and the intensity of fluorescence was much decreased, especially the fluorescence below 400nm, after nanosecond laser conditioning. Moreover, the intensity of fluorescence could be further decreased after sub-nanosecond laser conditioning. The slightly variation of Raman scattering proved the modification of the PO4 vibrational modes. The sharply decrease of fluorescence intensity below 400 nm reflected the density reduction of electron defects in these crystals. On the basis of the above analysis, laser conditioning mechanism in DKDP crystals was discussed.